I'm using Atomz in my site. They have a couple of types of search scripts, I have the more simple of the two. The other provides for a more detailed search. You get a search result that looks similar to Google...and you get a report each week that provides the most common keyword searches conducted for the past week. Take a peek at my site to see how it works. You can check my wife's site at:

http://www.moms-kitchen.com/

...to see an example of the detailed search. Hope this helps.